1. Field of the Invention
This invention relates to an abrasive shaped article used for polishing a substrate material such as a silicon wafer and an oxide substrate, and an optical material; an abrasive disc comprising the abrasive shaped article; and a polishing method. More particularly it relates to an abrasive shaped article made by shaping an ultrafine silica powder into a shaped article, and sintering the shaped article; an abrasive disc comprising the abrasive shaped silica article and a supporting auxiliary; and a polishing method using the abrasive shaped silica article.
2. Description of the Related Art
In a process for polishing a substrate material such as a silicon wafer or an oxide substrate, a loose abrasive polishing procedure has heretofore been employed wherein the substrate material is polished with a polishing pad made of nonwoven fabric or suede cloth, while a polishing liquid comprising a loose abrasive grain such as colloidal silica or cerium oxide, and a chemical such as potassium hydroxide is continuously supplied onto the substrate material. For example, it is described in Japanese Unexamined Patent Publication (abbreviated to "JP-A") 5-154760 and JP-A 7-326597 that a silicon wafer is polished with a polishing cloth and a loose abrasive grain. In the conventional loose grain polishing procedures using a loose grain-containing polishing liquid, a salient amount of a waste polishing liquid containing a loose grain is produced during polishing, and therefore, the efficiency of the polishing procedure, equipment for waste disposal and environmental pollution with the waste polishing liquid must be considered. The polishing pad such as polishing cloth is liable to be clogged and the polishing performance is deteriorated, and thus the polishing pad must be often renewed and the polishing efficiency is decreased.
Further, the conventional polishing procedure using a polishing pad has a problem such that the surface of the polishing pad is pliable and therefore the entire surface of a material to be polished is not uniformly abraded, i.e., the corner portions of the material surface are excessively abraded upon polishing.
To sum up, the conventional polishing procedure using a polishing pad and a loose abrasive grain bears problems in the disposal of waste polishing liquid, the working efficiency of polishing, and the uniformity in abrasion of the entire material surface to be polished.